1. Field of the Invention
The present invention relates generally to improved methods of stimulating wells in unconsolidated formations, and more particularly, to methods of stimulating fluid production from such wells while reducing or preventing the migration of sand with the fluids produced therefrom.
2. Description of the Prior Art
Oil and gas wells are often completed in unconsolidated formations containing loose and incompetent sands which migrate with oil, gas and/or water produced by the wells. The presence of sand in the produced fluids is disadvantageous and undesirable in that the sand particles abrade pumping and other producing equipment and reduce the fluid production capabilities of the producing zones in the wells.
Incompetent subterranean formations include those which contain loose sands that are readily entrained by produced fluids and those wherein the sand particles making up the formations are bonded together with insufficient bond strength to withstand the forces produced by the production of fluids from the formations. A technique which is often used for minimizing sand production from such formations is to produce fluids from the formations at low flow rates whereby the near well stabilities of sand bridges and the like in the formations are preserved. However, the collapse of such sand bridges often occurs as a result of unintentional high production rates and pressure surging.
Heretofore, producing zones in unconsolidated formations have been treated by creating fractures in the zones and depositing hardenable resin composition coated proppant in the fractures to maintain the fractures in open positions. The hardenable resin composition coating on the proppant is caused to harden after the coated proppant has been deposited in the fractures thereby consolidating the proppant into hard permeable masses therein which reduces or prevents the migration of sand through the fractures with produced fluids.
A problem which accompanies the use of resin composition coated proppant in fractures formed in unconsolidated formations involves the excess coated proppant which is left in the well bore after coated proppant is deposited in the fractures. The excess resin composition coated proppant settles in the well bore adjacent to the fractured zone and hardens into a hard permeable mass therein. As a result, it has heretofore been necessary to drill out the hardened resin composition coated proppant in the well bore in order to allow produced fluids to more freely flow into the well bore from the fractures and to provide access to the producing interval in the event it is necessary to carry out remedial procedures therein.
Thus, there is a need for improved methods of stimulating wells formed in unconsolidated hydrocarbon producing formations whereby excess hardened resin composition coated proppant remaining in the well bore is easily and inexpensively removed.